X2 caps

[22mannightstar]

I need 5 or 6 X2 caps of .01uf at somewhere around 400v value with long leads. does anybody have a source?

 

[DF96]

400V (not 400v) is probably a DC voltage rating, not a value. X2 caps are AC rated, not DC rated - although they may sometimes have a DC rating too.

0.01uF (not .01uf) is a typical X2 value so you should find them in any decent electronics catalogue.

Long leads might be a problem. Why do you need long leads?

 

[22mannightstar]

I need long leads to cross the AC lines on a bridge rectifier

 

[DF96]

You could add some extra wire, or use a small subsidiary PCB or tagstrip.

Sadly, long lead components are becoming more rare.

 

[22mannightstar]

Bummer, I'll probably have to solder some lead on to make them longer although I don't like doing that.

 

[rayma]

Bummer, I'll probably have to solder some lead on to make them longer although I don't like doing that.

Digikey has plenty of Kemet and Panasonic X and Y caps with long leads. An example:
http://www.digikey.com/product-detail/en/PHE820MB5100MR17/399-7601-ND/3465773

 

[22mannightstar]

I need 400V or 440V

 

[rayma]

I need 400V or 440V

What will be the actual AC voltage across the X2 capacitor?

 

[22mannightstar]

I'll have to wait until I get my amp reassembeled and fire it up and check it.

 

[DF96]

I need 400V or 440V

Why?

 

[22mannightstar]

Actually I could have used less but I wanted a safety margin and you get wide gaps in the VR of these caps ie 275, 305, 310 but after that its hard to find anything until you get to 400V or 440V. I just settled on the highter number rather than the lower one.

 

[DF96]

The design of an X2 cap already includes a safety margin, so you don't have to include one too. You just pick one appropriate to your mains voltage. They are failsafe, which often means that they slowly lose capacitance over a number of years.

 

[Speedskater]

I need long leads to cross the AC lines on a bridge rectifier

I hope that the bridge rectifier is on the secondary side of the transformer. A typical X2 capacitor is on the primary side of the transformer.

 

[DF96]

You don't need an X2 cap on the secondary side, as failure here has less catastrophic consequences than a short across the mains. Just pick a cap with DC rating about twice the peak AC voltage.

 

[AndrewT]

What is the secondary voltage of the transformer?
What is the worst case (highest) voltage that one could get from that transformer?

Multiply that worst case value by sqrt(2).

Select a capacitor that can take that 1.4times highest voltage.

eg dual secondary 25+25Vac, has a worst case output of ~254/230*(25+25)*(1+regulation) ~ 60Vac
Times 1.4 equals 85V

Select a capacitor that can take >=100V
It will never fail due to overvoltage.

 

[22mannightstar]

You don't need an X2 cap on the secondary side, as failure here has less catastrophic consequences than a short across the mains. Just pick a cap with DC rating about twice the peak AC voltage.

O.K. guys, this is across the secondary and I have those caps handy, I will use them. I added something new to my quite limited electronic knowledge.

I couldn't see why it would make any difference as to cap quality because AC noise is AC noise but I see now.

 

[29285]

I need long leads to cross the AC lines on a bridge rectifier

You want to parallel the x-cap to your anode winding of mains transformer? Why that?

 

[AndrewT]

You want to parallel the x-cap to your anode winding of mains transformer? Why that?

Our poster has not told us he has an anode.
He has not told us what he needs.
He has told us what he wants.

 

[29285]

I need long leads to cross the AC lines on a bridge rectifier

Combining this with the first posting I conclude this is the high-voltage winding of some tube amp mains transformer. Ok?

 

[AndrewT]

not OK.